Alfred Bell — 'Post-glacial Drifts of Ireland. 451 



In the interesting paper by Prof. Harkness ^ I find the following 

 remarks, that I cannot agree with, and respectfully urge upon the 

 author to reconsider them. He says, " There are several locali- 

 ties in Ireland where beds, having the same nature and affording 

 precisely the same contents as the Manure Grravels of the Co. 

 Wexford are to be found," and the type locality selected by the 

 Professor is that one of which the Fauna is best known. 



The age of the Wexford beds is a vexed question, and its relations 

 to other localities can only be settled by the fossils. 



The beds in debate extend from Arklow along the whole line of 

 coast to Kilmore, and inland to Gorey and Enniscorthy, altogether 

 about 40 miles long by 8 or 9 broad, and consist of fine gravels 

 capped by Boulder-clay, full of striated stones. On the coast the 

 clay is described by Capt. James as resting upon a deposit of rolled 

 and waterworn pebbles, the foundation rock not being visible. The 

 deposit had been quietlj^ accumulated, giving time for the successive 

 growth of layers of stony Nullipore. In the gravel (or gravelly 

 clay, for the character of the deposit is not precisely laid down) 

 shells abound". 



From the gravels being capped by Boulder-clay Prof. Harkness 

 appears to identify these beds with those further north, where the 

 same general arrangement is shown in the cliffs upon the sea-shore. 

 But this evidence is not of much value when set against the diver- 

 gence of the Faunas, which I shall show presently is so well marked. 

 It may be worth while to call to notice thrat at Bohernabreena, Co. 

 Dublin, the fossiliferous drift rests upon the Corn or Limestone gravel, 

 which in its turn overlies a stiff clay very prevalent in Dublin, 

 Meath, and Kildare, and I am disposed to think that this stiff clay 

 may be the equivalent of the clay which Prof. Harkness found 

 overlying the Wexford gravels. This I need not enter upon now, as 

 I rest my case upon the fossils of the two localities, viz. those of 

 Wexford and those selected by the Professor ; but I may notice that 

 in Co. Wicklow, the deposits are perfectly laminated and regularly 

 bedded, and contain entire shells, the covering bed being the Boulder- 

 clays. 



Of the 69 species of shells recorded from the Wexford beds, 52 

 still live in the Biitish seas ; 47 of that number being also present 

 in the antecedent Crags, and may therefore be left out of the question. 

 Of the others ten are high northern forms, one Japanese, four southern, 

 and two of which the habitat (if still living) is unknown. 



Now if the age of the Dublin Drifts at Howth, Glenismaule, 

 Bohernabreena, Killiney, and Bray are the same as that of Wexford, 

 we ought to find the Wexford fossils in some of these localities to 

 justify the statement that the contents are the same ; but the fact is 

 that only one of the following extra British species {fieda ohlonga) 

 occurs in the Dublin beds. Three others, Astarte horealis, Trophon 

 claihratus, and Natica affinis, are present in the equivalent West of 

 England Drifts; but all the four species are now living on the verge 

 of the British seas. 



1 Geol. Mag., Vol. VI., p. 542. 



